1. Field of the Invention
The present invention relates to a semiconductor device and a method of producing the semiconductor device, in particular, to a semiconductor device having a contact structure utilizing a multi-layer conductive plug and a method of producing the semiconductor device.
2. Discussion of Background
In recent years, a size of a contact hole is reduced along with microminituarization of a semiconductor integrated circuit. As a result, it becomes difficult to form a resist pattern, and etching using this resist pattern as a mask becomes difficult by an increment of an aspect ratio of the contact hole.
In order to reduce the aspect ratio and a load in etching, there has been proposed a method of obtaining a contact structure by dividing an inter-layer insulating film into multi layers, forming a contact hole in each of the multi layers, and vertically connecting conductive plugs embedded in the contact holes.
However, according to these methods, misregistration between the horizontally arranged contact holes is apt to occur, an insulating film in a lower layer is etched at time of forming the contact hole in an insulating film in an upper layer by etching. Further, in a worse case, the contact hole in the upper layer reaches an electrode layer located in the insulating film in the lower layer, whereby an electric short is caused.
In order to solve such a problem, in Japanese Unexamined Patent Publication JP-A-8-37181, a contact structure, in which an etching prevention film is interposed between an insulating film in an upper layer and an insulating film in a lower layer, is disclosed.
In other words, in reference of a cross-sectional view in a step of a process illustrated in FIG. 22 of the above JP-A-8-37181, even though an upper insulating film 108 is disposed on a lower insulating film 104 through an etching prevention film 105, and succeedingly an upper layer contact hole 109 formed on the upper insulating film 108 is deviated from a lower contact hole 106 so that a part of the upper contact hole 109 reaches a lower layer insulating film 104 by etching, the lower layer insulating film 104 is not etched, whereby the upper layer contact hole 109 does not reach electrode layers 103a, 103b on a semiconductor substrate 101.
However, in a conventional technique disclose in the above JP-A-8-37181, when a semiconductor device is further integrated and a size of a contact hole is further microminiaturized, a good contact hole cannot be formed because dimensional controllability and a shape of a resist pattern, which is formed on an etching prevention film, are deteriorated. Therefore, there are problems that a dimensional accuracy and a shape of a conductive plug formed in the contact hole are deteriorated, and a stable electrical connection between upper and lower conductive plugs is not obtainable.
Incidentally, in the above JP-A-8-37181, a method of forming the etching prevention film after forming the conductive plug is disclosed. According to such a process, it is possible to prevent the etching prevention film from thinning at time of forming the conductive plug by etching.
In other words, in reference of a cross-sectional view explaining a step of a process of manufacturing the semiconductor device, after forming the lower layer insulating film 104 including a conductive plug 107 formed in the lower layer contact hole 106, an etching prevention film 124 is formed, and further an insulating film 108 including an upper layer contact hole 109 is formed on the etching prevention film 124. The etching prevention film 124 prevents etching to the lower layer insulating film 104 when the upper layer contact hole 109 is formed with a deviation from the lower layer contact hole 106. Thereafter, as illustrated in FIG. 23(b), the etching prevention film 124 exposed inside the upper layer contact hole 109 is etched so as to be connected to the lower layer film conductive plug 107. Thereafter, an upper layer conductive plug 110 is embedded in an upper layer contact hole 109 so as to be connected to the lower layer conductive plug 107.
However, in such a method of forming, as illustrated in FIG. 24(a), a problem occurs when a surface of the lower layer conductive plug 107 is formed with a large drop 172 with respect to a surface of the lower layer insulating film 104. Namely, the etching prevention film 124 has an uneven shape reflecting a shape of the drop. When the upper layer insulating film 108 and upper layer contact hole 109 connected to the conductive plug 107 are formed, there are problems that a part of the etching film 124 which is formed on a side surface of the drop 172 is left on the conductive plug 107 as a residue 182, and a contact resistance between the upper layer conductive plug 110 embedded in the upper layer contact hole 109 and the lower layer conductive plug 107 is increased as illustrated in FIG. 24(b).
A reason why the drop 172 occurs in the conductive plug 107 is to over-etch or over-polish so that the conductive plug is securely embedded in an entire area of a wafer surface in consideration of uniformity of a film thickness on a surface of the wafer at time of forming the conductive plug or uniformity of an etching rate or, uniformity of polishing rate on the wafer surface.
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide a semiconductor device having a contact structure comprising multi-layer conductive plugs, by which a short between the conductive plug and an electrode layer is prevented, and an electrical connection between upper and lower conductive plugs is stabilized to improve the reliability.
Another object of the present invention is to provide a semiconductor device including a contact structure of a capacitor comprising multi-layer conductive plugs, by which shorts between a capacitor electrode and an electrode layer and between the conductive plug and the electrode layer are prevented, and an electrical connection between upper and lower conductive plugs is stabilized to improve reliability.
Another object of the present invention is to provide a semiconductor device including a multi-layer wiring structure using a conductive plug, by which a short between the conductive plug and an electrode layer is prevented and an electrical connection between the conductive plug and a wiring layer is stabilized to improve reliability.
Another object of the present invention is to provide a method of producing a semiconductor device including a contact structure comprising multi-layer conductive plugs, by which a short between the conductive plug and an electrode layer is prevented, and a contact resistance between upper and lower conductive plugs is reduced.
According to a first aspect of the present invention, there is provided a semiconductor device comprising an electrode formed on a part of a semiconductor layer, a first insulating layer including a first insulating film and a first anti-reflection coating formed on the first insulating film, a first contact hole formed in the first insulating layer and reaching the semiconductor layer by penetrating a vicinity of side surface of the electrode layer from a surface of the first insulating layer, a first conductive plug embedded in the first contact hole and electrically connected to the semiconductor layer, a second insulating layer formed by covering the first insulating layer and the first conductive plug, a second contact hole formed in the second insulating layer and reaching the first conductive plug and the first insulating layer from a surface of the second insulating film, a second conductive plug embedded in the second contact hole and electrically connected to the first conductive plug, and a conductive layer formed in the second conductive plug and electrically connected to the semiconductor layer through the first conductive plug and the second conductive plug.
According to a second aspect of the present invention, there is provided the semiconductor device, wherein the second insulating layer includes a second insulating film and a second anti-reflection coating formed on the second insulating film.
According to a third aspect of the present invention, there is provided the semiconductor device, further comprising a third insulating layer formed by covering the second insulating layer and the second conductive plug, and an opening provided in the third insulating layer, which opening reaches the second conductive plug from a surface of the third insulating layer, wherein the conductive layer is a capacitor electrode electrically connected to the semiconductor layer through the first conductive plug and the second conductive plug and formed in the opening.
According to a fourth aspect of the present invention, there is provided the semiconductor device comprising an electrode layer formed on a part of a semiconductor layer, a first insulating layer formed by covering the semiconductor layer and the electrode layer and by sequentially laminating a first insulating film and a first anti-reflection coating, a first contact hole formed in the first insulating layer and reaching the semiconductor layer by penetrating a vicinity of a side of the electrode layer from a surface of the first insulating layer, a first conductive plug embedded in the first contact hole and electrically connected to the semiconductor layer, a first wiring layer electrically connected to the semiconductor layer through the first conductive plug and formed on the first conductive plug, a second insulating layer formed by covering the first insulating layer and the first wiring layer, a second contact hole formed in the second insulating layer and reaching the first wiring layer and the first insulating layer from a surface of the second insulating layer, a second conductive plug embedded in the second contact hole and electrically connected to the first conductive layer, and a second wiring layer electrically connected to the first wiring layer through the second conductive plug and formed on the second conductive plug.
According to a fifth aspect of the present invention, there is provided the semiconductor device, wherein the second insulating layer includes a second insulating film and a second anti-reflection coating formed on the second insulating film.
According to a sixth aspect of the present invention, there is provided the semiconductor device, wherein the first anti-reflection coating and second anti-reflection coating are a silicon oxynitride film.
According to a seventh aspect of the present invention, there is provided a method of producing a semiconductor device comprising steps of: forming an electrode layer on a part of a semiconductor layer, forming a first insulating layer on the semiconductor layer and the electrode layer by sequentially laminating a first insulating film and a first anti-reflection coating, forming a resist film having a predetermined pattern on the first anti-reflection coating, etching the first insulating layer using the resist film as a mask and forming a first contact hole reaching the semiconductor layer by penetrating a vicinity of a side surface of the electrode layer, embedding to form a first conductive plug electrically connected to the semiconductor layer in the first contact hole, forming a second insulating layer on the first insulating layer and the first conductive plug, etching to form a second contact hole reaching the first anti-reflection coating and the first conductive plug in the second insulating layer using the first anti-reflection coating as an etching prevention film with respect to the first insulating film, embedding to form a second conductive plug electrically connected to the first conductive plug in the second contact hole, and forming a conductive layer electrically connected to the semiconductor layer through the first conductive plug and the second conductive plug on the second conductive plug.
According to an eighth aspect of the present invention, there is provided the method of producing the semiconductor device, wherein the step of forming the second insulating film includes a step of forming the second insulating film and a second anti-reflection coating by sequentially laminating these and a step of etching to form using a resist film formed on the second anti-reflection coating as a mask.
According to a ninth aspect of the present invention, there is provided the method of producing the semiconductor device further comprising steps of: forming a third insulating film on the second insulating layer and the second conductive plug, etching to form an opening reaching the second conductive plug using the second anti-reflection coating as an etching prevention film with respect to the second insulating film, wherein the conductive layer is a capacitor electrode formed in the opening and electrically connected to the semiconductor layer through the second conductive plug and the first conductive plug.
According to a tenth aspect of the present invention, there is provided the method of producing the semiconductor device, wherein the anti-reflection coatings are a silicon oxynitride film.
According to an eleventh aspect of the present invention, there is provided a method of producing a semiconductor device comprising steps of: forming an electrode layer on a part of a semiconductor layer, forming a first insulating layer on the semiconductor layer and the electrode layer, forming a first contact hole reaching the semiconductor layer by penetrating a vicinity of a side surface of the electrode layer in the first insulating layer, embedding to form a first conductive plug in the first contact hole, the first conductive plug is electrically connected to the semiconductor layer and a surface of the first conductive plug is recessed from a surface of the first insulating layer, processing to flatten the surfaces of the first insulating layer and the first conductive plug, forming a first etching prevention film on the flatten first insulating layer and the flatten first conductive plug, forming a second insulating layer on the first etching prevention film, forming a second contact hole reaching the first etching prevention film at a position overlapping at least the first conductive plug in the second insulating layer, etching the first etching prevention film exposed to a surface of the second contact hole and connecting the second contact hole to the first conductive plug, embedding to form a second conductive plug electrically connected to the first conductive plug in the second contact hole, and forming a conductive layer electrically connected to the semiconductor layer through the first conductive plug and the second conductive plug on the second conductive plug.
According to a twelfth aspect of the present invention, there is provided the method of producing the semiconductor device further comprising steps of: processing to flatten surfaces of the second insulating layer and the second conductive plug, forming a second etching prevention film on the flattened second insulating layer and the flattened second conductive plug, forming a third insulating layer on the second etching prevention film, forming an opening reaching the second etching prevention film at a position overlapping at least the second conductive plug in the third insulating layer, etching the second etching prevention film exposed to a surface of the opening and connecting the opening to the second conductive plug, wherein the conductive layer is a capacitor electrode formed in the opening and electrically connected to the semiconductor layer through the first conductive plug and the second conductive plug.